I. Field of the Invention
The present invention relates to equipment for intercepting and diverting a liquid circulation flow and the relative interception and diversion process.
II. Description of Related Art
This equipment can be used for exerting the function of diverting for safety purposes, during the insertion of a new drill string, the mud flow towards the device, called E-CD, described in patent application IT-MI2005A001108 of the same applicant, without influencing the Rig Pump Manifold of the Rig Contractor which therefore maintains its functional characteristics intact (it does not wear and is not modified).
Ever since the beginning of drilling called “rotary drilling” which dates back to over a century ago, which had replaced the advance technique called “percussion” in use at that time, introducing the novelty principle of the use of drill rods for transmitting the rotary movement to the bit (associated with the pumping of a fluid into the well through the same “battery” of rods), there has been the problem of interrupting the pumping process every time it was necessary to add a new rod to the battery, for drilling.
This time transitory, identified from the moment in which the pumping of fluid into the well is interrupted to the moment in which the pumping action into the well is re-started, after adding a new single element to the battery of rods, has always been considered a critical period. This critical period remains until the condition existing at the moment prior to the interruption of the pumping of fluid into the well has been re-established.
Some of the undesired effects caused by the conventional interruption of the fluid circulation in wells, during the insertion and connection, or disconnection, process of an element in a drill battery, are listed hereunder:                there is a lack of dynamic pressure induced in the well by the circulation and its effect conventionally defined ECD (Equivalent Circulating Density) diminishes;        the dynamic pressure induced at the well bottom is annulled, favouring the potential entry of layer fluids in the well (kick);        when the circulation is restarted, after the rod has been added using a conventional method, troublesome overloads can be created of the more receptive formations, or potential circulation losses in the weaker formations;        in high verticality wells the unobstructed and rapid falling of drill cuttings can cause “mechanical blockage” conditions of the drill battery (BHA);        in the presence of wells with a high slope angle, in extended reach wells and in wells with a horizontal development, the drill cuttings have sufficient time to deposit on the lower part of the hole;        at the drilling restart, after the insertion of a new rod, the bit is “compelled” to re-perforate the bed of deposited cuttings at the well bottom, before being able to reach the virgin formation once again.        
As specified above, in patent application IT-M12005A001108, the same applicant claimed a device, called E-CD, which allows the pumping and consequently the fluid circulation in the well to be kept constantly active, during all the operative steps, necessary for effecting the addition of a new “single element” to the battery of rods, which allows drilling to be effected to a greater depth.
With the same procedure, it is possible to effect the reverse process, allowing the bit to be extracted without interrupting the pumping of fluid into the well.
The key result which is obtained from this operative opportunity offered by the device is the elimination (or abatement) of all the critical aspects implied in the traditional process for adding or subtracting rods from the drill battery.
A description is provided hereunder of the E-CD device and the process for the insertion of a new drill string already described in patent application IT-MI2005A001108 cited above.
The device for the insertion of a new drill string essentially consists of a short body (C) in the form of a pipe having, at its ends, means suitable for being screwed onto drill rods, in which two valves are housed, of which one (A) is radial to said short body, which can be intercepted from the outside by means of an adapter and equipped with an appropriate safety top, preferably pressure-sealed, the other (B) axial to said body.
The result is a system of valves which allows direct contact to be made with the fluid pumped into the well through the drill battery, at any moment desired and in both directions of the descending fluid (radially and axially).
The short body of the device preferably has a length ranging from 50 to 100 cm.
The valve (A), which is radial to the drill battery, can be intercepted from the outside by means of a suitable adapter (for example a rapid connector), in turn coupled with a flexible pipe, whose function is to interconnect the device with the well pumping system (“Rig pump manifold”), of the drill plant itself.
As a consequence, the valve (B) which is axial to the drill battery and has characteristics of “bidirectional reactivity sensitivity” to the pressure to which it is subjected (therefore sensitive to the flow state of the drill fluid pumped into the well), in turn closes and opens directionally with respect to the fluid.
Both the radial valve (A) and the axial valve (B) are preferably butterfly valves, more preferably preloaded with springs, which are closed when in stand-by.
In short, the configuration of the two valves housed in a short body, as described so far, allows a flow of drill fluid to be easily kept uninterrupted towards the well, during all the operative steps necessary for effecting the addition of a new “single rod element” (or series of rods) to the drill battery, which allows drilling to be effected to a greater depth.
Apart from the conceptual and constructive simplicity, one of the intrinsic advantages of the device described above is that it can be immediately used by any drill plant, without requiring heavy modifications to the hydraulic circuit of the plant itself, or problems associated with the “vertical spatiality” for the insertion of the tool into the drill battery.
The device can be used in any type of plant existing in the world—with no exception—whether it be extremely obsolete or completely modern, whether it be equipped with the traditional “Rotary Table System” or more modern “Top Drive System”, in both onshore and offshore well drilling.
Higher operating pressures can obviously be obtained by selecting higher-quality single components, to assemble the desired component.
There are numerous benefits deriving from the fact of not interrupting the circulation, and they can vary each time in relation to the type of well to which the procedure is applied.
In any case, the benefit which is common to all types of wells is the resulting constant pressure state on the walls of the hole and at the well bottom, which provide valuable intrinsic safety.
Let us examine in particular High Pressure and High Temperature Wells (HPHT).
In this type of well, the fracturing gradient of the formations penetrated, close to the mineralized rock (reservoir), is generally close to the value of the pore gradient. For this reason, a careful control of the ECD (equivalent circulating density) is compulsory to avoid circulation losses and structural weakening of the formation itself.
During interruptions in the circulation (necessary for effecting a conventional connection), the ECD is annulled, creating the ideal condition for the undesired entry of state fluid into the well (influx).
The influx can come directly from the reservoir (primary porosity) or from induced microfractures; in any case observation of the phenomenon (and the identification of the condition necessary for a new connection) implies a waste of operative and consequently unproductive time.
The “uninterrupted circulation” by means of the device described above, on the contrary, guarantees undisturbed dynamic conditions, allowing the safe and immediate insertion of a new rod, without any time losses.
Let us examine in particular the application for drilling defined as under Balance/Close to Balance Drilling (UBD).
For Underbalance drilling (UBD) and its derivatives, it is crucial to maintain a stable and controlled condition of the pressure regime, distributed on the walls of the hole as also on the well bottom.
The loss of this condition can jeopardize what has so far been effected upstream for UBD drilling. The addition of a rod to the drill battery is a particularly critical moment; the use of the device described above eliminates all critical aspects as soon as they arise, as it always guarantees undisturbed dynamic conditions, allowing the safe and immediate insertion of a new rod, without any time loss. The guarantee of maintaining a stable and constant pressure regime on the walls of the hole and well bottom, avoids the accumulation of gas cushions and “packs” of cuttings which would require non-productive time for eliminating them and re-establishing the stabilized conditions prior to the interruption of the circulation. An error in the running of this process leads to the risk of thwarting the whole UBD well project, activating an undesired accidental well killing.
An alternative to the use of the device can be to directly integrate the valve system forming the device itself in the construction phase of the drill rod; this alternative allows the length of the combination (rod+device) to be kept identical to that of a nude rod, should the necessity arise.
In any case, composed lengths of drill rods equipped with the device, will house the system at the head of any length. An alternative to the device can therefore be a drill rod essentially consisting of a pipe having suitable threadings at the ends to be screwed onto other drill rods, in which two valves are housed of which one (A) radial to said pipe, which can be intercepted from the outside by means of an adaptor and equipped with a suitable safety top, preferably pressure sealed, the other (B) axial to said pipe.
Both the radial valve (A) and the axial valve (B) housed in the rod are preferably butterfly valves, more preferably preloaded with springs, which are closed in stand-by.
The process for the insertion of a new drill string consists in using the devices described above or alternatively the drill rods described above in which there are radial and axial valves.
More specifically, this process preferably comprises the following steps:                intercepting from the outside and connecting by means of suitable means to the pumping system of the drill plant, the radial valve (A) of the short body or drill rod by means of a suitable connector;        voluntarily interrupting the flow of primary fluid, through the injection head, at the inlet in the drill battery with the consequent passage of the flow only from the radial valve (A) and with the consequent closing of the axial valve (B);        inserting a new drill string on the short body or drill rod, coupled with another short body in which said valves are housed or a new drill string containing a drill rod in which said valves are housed;        re-establishing the flow of primary fluid with the consequent opening of the axial valve (B) and consequent closing of the radial valve (A);        disconnecting the connector and protecting the radial valve (A) with a safety top;        lowering the drill battery.        
Lastly, the final result of the operative steps described allows the insertion and connection process of an element in a drill battery (single rod or length) to be obtained, with a full flow-rate and without any interruption of the continuity.
From what is indicated above the term E-CD device in the present patent application comprises both the device and the drill rods, in which radial and axial valves are present, which form an alternative, claimed in patent application ITMI2005A001108.